The disclosed technology relates generally to decreasing the bit- and/or symbol-error rate of multiple-input multiple-output (MIMO) communications systems, and more particularly, to improving the decoding performance of such systems using incremental redundancy (IR) hybrid automatic repeat-request (HARQ) transmission techniques with symbol vector-level decoding.
Multiple-input multiple-output communication systems (e.g., communications systems using multiple transmit and/or receive antennas) have proven useful in addressing a wide array of challenges in current and next-generation wireless systems. For example, MIMO systems have been shown to provide resiliency to interference, rapid mobility, and/or deep fades in channel quality. Additionally, MIMO technology is often used with HARQ transmission, for example Chase combining and IR techniques, to improve transmission throughput while reducing the number of bits needed to decode each received codeword. For example, MIMO IR HARQ techniques have been adopted in a wide variety of standards, including WiMAX, LTE, and HSDPA/HSUPA.
However, MIMO IR HARQ systems may use receiver structures in which data is decoded sub-optimally, thereby decreasing the decoding bit- and/or symbol-error rate relative to an optimal receiver structure. Such sub-optimal designs may reduce application quality and/or increase system latency. Therefore, there exists a need for optimal, or nearly-optimal, decoding strategies for use in MIMO IR HARQ systems. In particular, there exists a need for optimal or near-optimal symbol vector-level combining techniques for use in MIMO IR HARQ wireless systems.